Block Adware using Windows Defender

Typically, Windows Defender is an antivirus tool which is made by Microsoft, and commonly included in all operating systems since Windows 7. However, the program didn’t have adware detection and blockage by default since the inauguration of this software, but Microsoft later added this functionality as the number of demand was going too high and Microsoft really wanted to enhance the features of the built in Windows security tool.


According to a latest announcement made by Microsoft in late November, 2015, the Microsoft Enterprise customers are bound to receive the ability to offer additional protection against PUAs; abbreviation standing for Potentially Unwanted Applications. However, though the official release has been done for the Enterprise consumers only, a Windows user can enable the feature on Windows Defender despite being a home or SOHO user. Some registry tweak would be required.

PUA Activation in Windows Defender

Basically, the user needs to enable PUA in Windows Defender if they want to block adware programs, because they are basically potentially unwanted applications. Windows Defender on Windows 8, Windows 8.1 and Windows 10 would support the inclusion of PUA into the system. Before you begin with the process, it is required that a whole backup of the Windows registry is taken and kept somewhere else, in case anything goes wrong and a restoration is required. Also, have backups of important user files.

Once the pre-tweak tasks are done, proceed with the steps as mentioned below.

  • From the Run dialog box, type regedit and launch Registry Editor. To launch Run, press Windows key and R button simultaneously, the Run window will show up and type in regedit.
  • The UAC might appear, asking for necessary permissions to edit the Registry. Confirm if the dialogue box appears.
  • From the left pane where expandable titles are present, navigate to HKEY_LOCAL_MACHINE. Expand the options and navigate straight towards Software> Policies> Microsoft> Windows Defender.
  • Once you reach Windows Defender, right click on the folder and from New, click on Key.
  • Name the new key as MpEngine. Some values need to be added to this key so that Windows knows what processions are expected from the key.
  • Right click on MpEngine and click on New again, then add a Dword (32 bit) value.
  • MpEnablePlus will be the name for the new key that’s created, and set the value to 1 for this new key.
  • Exit Registry Editor. Now restart the computer using the regular button inside Windows.

Windows Defender has now been given with the ability to block Potentially Unwanted Applications. Any PUA will not be downloaded into the system from now on, however Internet Explorer or Microsoft Edge must be used for Internet downloads for this feature to work. However, regular protection will always work if Windows Defender is turned on and activated.


If you feel Potentially Unwanted Application feature isn’t working out for you, then it could easily be deactivated from the Registry Editor. Navigate to the key you have created following the above method, and set the MpEnable Plus Dword value to 0. If you want to completely undo the action, delete the whole key from the Registry.


This is how a user can block adware using Windows Defender without investing on third party programs. However, third party programs might offer additional features which Windows Defender probably won’t.

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Kevin Clark

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